Ardipithecus and Australopithecines

• Fossil evidence exists for Ardipithecus and Australopithecines

Ardipithecus

• Includes Ardipithecus Ramidus from Ethiopia, dating back 4.4 million years ago.
• Possible hominin ancestor, sister ancestor, or has evolutionary connections to Miocene apes and australopithecines.
• Determination of bipedalism is based on the forward position of the foramen magnum.
• Lived in forests, not savannahs
• Had a more primitive dental pattern with large canines.

Australopithecines

• Includes species such as A. Anamensis, A. afarensis, A. Bahrelghazalia, A. africanus, A. garhi, and A. aethiopicus.
• Robust forms include A. robustus and A. boisei.
• A. Anamensis dates to 4.2 million years ago, found in 1995 at east Turkana sites.
• Had large canines but with thicker enamel, more hominin-like.
• Its postcranial skeleton suggests bipedalism.
• Lived in savannah and woodland areas.
• Ancestral to all later hominins?
• A. Afarensis: "Lucy", discovered in Hadar in 1974.
• Almost 40% of the skeleton was recovered.
• Notable features of locomotion: long fingers and toes, long upper limbs, and short lower limbs.
• It may have been an efficient climber who spent time in trees, with a habitual bent-knee/bent-hip gait on the ground.
• Forward-projecting face, large canines (smaller relative to apes) with a diastema, and a hint of a sagittal crest.
• A. Bahrelghazalia: Found in Chad (North Central Africa) in 1995.
• Another hominin species existed at the same time as A. Afarensis.

A. Africanus

• Discovered in 1924 in South Africa.
• The "Taung Child" was determined based on teeth formation and eruption.
• Less forward-projecting face (prognathic) than A. Afarensis.
• Dental proportions: larger molars, smaller canines.
• No sagittal crest with smaller teeth.
• Limb proportions are less ape-like than A. Afarensis.

A. Garhi

• Found in 1999 in the Afar region of Ethiopia.
• Possible tool-using hominin.
• Its place in the evolutionary line toward Homo is questioned.
• Small cranium, projecting ape-like face.

A. Aethiopicus

• Much more robust with large jaws and teeth, and a very present sagittal crest.
• "The Black Skull" from Koobi Fora, Kenya.
• Smallest adult hominin cranial capacity.
• Body size comparable to other australopithecines.
• Believed to be Paranthropus genus

Robust Australopithecines

• Exhibit robust teeth and jaws, indicating chewing specializations.
• A. Robustus found in South Africa.
• A. Boisei
• Recall emergence of hominins

Genus Homo

• Showed up in Plio-plesitocene period
• By 2.5-2 mya, Miocene drying trend intensified.
• In Africa, extinctions and new species emerged.
• Gracile Australopithecine evidence disappears.
• Evolved into or were replaced by a new type of hominin with a larger brain size.
• Australopithecines range from 400-500 cc, while new hominins are over 600cc.
• Coexisted with Australopithecus Boisei.
• Early examples of the genus Homo.
• Homo habilis ("the handy man").
• Discovered at Olduvai (1963, Louis Leakey).
• 600cc cranial capacity

Homo Habilis

• Leakey believed the increase significant enough to be homo.
• cutoff should be midway between largest gorilla and smallest human cranial capacity = 750 cc
• Leakey decision was challenged
• 2.5-1.5 mya.
• First tool maker.
• Relatively prognathic face still but is declining.
• Some arboreality, living in trees
• Speech abilities questioned due to lack of physical evidence.
• Reduction in postorbital construction for expanded brain for Homo habilis.
• Differences are cranial traits (similar body size and shape).

Early Homo

• Suspect more than one species is classified as Homo habilis.
• Chris Stringer compared H. habilis cranial specimens at Olduvai and Koobi Fora.
• He found similarities in dental characteristics but differences in cranial volume, cranial shape, and face shape.
• New species designations?

Homo Rudolfensis

• 781cc.
• Discovered in 1972, Koobi fora.
• Contemporary of H. habilis (2.4-1.6 mya).
• Feet are more like modern humans than H. habilis.
• Teeth are relatively larger than H. habilis, indicating reliance on tougher foods.
• Placement is difficult: given a new species name in 1986.